@@ -54,6 +54,25 @@ void ovpn_crypto_state_release(struct ovpn_crypto_state *cs)
}
}
+/* removes the key matching the specified id from the crypto context */
+void ovpn_crypto_kill_key(struct ovpn_crypto_state *cs, u8 key_id)
+{
+ struct ovpn_crypto_key_slot *ks = NULL;
+
+ spin_lock_bh(&cs->lock);
+ if (rcu_access_pointer(cs->slots[0])->key_id == key_id) {
+ ks = rcu_replace_pointer(cs->slots[0], NULL,
+ lockdep_is_held(&cs->lock));
+ } else if (rcu_access_pointer(cs->slots[1])->key_id == key_id) {
+ ks = rcu_replace_pointer(cs->slots[1], NULL,
+ lockdep_is_held(&cs->lock));
+ }
+ spin_unlock_bh(&cs->lock);
+
+ if (ks)
+ ovpn_crypto_key_slot_put(ks);
+}
+
/* Reset the ovpn_crypto_state object in a way that is atomic
* to RCU readers.
*/
@@ -140,4 +140,6 @@ int ovpn_crypto_config_get(struct ovpn_crypto_state *cs,
enum ovpn_key_slot slot,
struct ovpn_key_config *keyconf);
+void ovpn_crypto_kill_key(struct ovpn_crypto_state *cs, u8 key_id);
+
#endif /* _NET_OVPN_OVPNCRYPTO_H_ */
@@ -255,6 +255,19 @@ void ovpn_encrypt_post(void *data, int ret)
if (likely(ovpn_skb_cb(skb)->req))
aead_request_free(ovpn_skb_cb(skb)->req);
+ if (unlikely(ret == -ERANGE)) {
+ /* we ran out of IVs and we must kill the key as it can't be
+ * use anymore
+ */
+ netdev_warn(peer->ovpn->dev,
+ "killing key %u for peer %u\n", ks->key_id,
+ peer->id);
+ ovpn_crypto_kill_key(&peer->crypto, ks->key_id);
+ /* let userspace know so that a new key must be negotiated */
+ ovpn_nl_key_swap_notify(peer, ks->key_id);
+ goto err;
+ }
+
if (unlikely(ret < 0))
goto err;
@@ -1094,6 +1094,70 @@ int ovpn_nl_key_del_doit(struct sk_buff *skb, struct genl_info *info)
return 0;
}
+/**
+ * ovpn_nl_key_swap_notify - notify userspace peer's key must be renewed
+ * @peer: the peer whose key needs to be renewed
+ * @key_id: the ID of the key that needs to be renewed
+ *
+ * Return: 0 on success or a negative error code otherwise
+ */
+int ovpn_nl_key_swap_notify(struct ovpn_peer *peer, u8 key_id)
+{
+ struct ovpn_socket *sock;
+ struct nlattr *k_attr;
+ struct sk_buff *msg;
+ int ret = -EMSGSIZE;
+ void *hdr;
+
+ netdev_info(peer->ovpn->dev, "peer with id %u must rekey - primary key unusable.\n",
+ peer->id);
+
+ msg = nlmsg_new(NLMSG_DEFAULT_SIZE, GFP_ATOMIC);
+ if (!msg)
+ return -ENOMEM;
+
+ hdr = genlmsg_put(msg, 0, 0, &ovpn_nl_family, 0, OVPN_CMD_KEY_SWAP_NTF);
+ if (!hdr) {
+ ret = -ENOBUFS;
+ goto err_free_msg;
+ }
+
+ if (nla_put_u32(msg, OVPN_A_IFINDEX, peer->ovpn->dev->ifindex))
+ goto err_cancel_msg;
+
+ k_attr = nla_nest_start(msg, OVPN_A_KEYCONF);
+ if (!k_attr)
+ goto err_cancel_msg;
+
+ if (nla_put_u32(msg, OVPN_A_KEYCONF_PEER_ID, peer->id))
+ goto err_cancel_msg;
+
+ if (nla_put_u16(msg, OVPN_A_KEYCONF_KEY_ID, key_id))
+ goto err_cancel_msg;
+
+ nla_nest_end(msg, k_attr);
+ genlmsg_end(msg, hdr);
+
+ rcu_read_lock();
+ sock = rcu_dereference(peer->sock);
+ if (!sock) {
+ ret = -EINVAL;
+ goto err_unlock;
+ }
+ genlmsg_multicast_netns(&ovpn_nl_family, sock_net(sock->sock->sk),
+ msg, 0, OVPN_NLGRP_PEERS, GFP_ATOMIC);
+ rcu_read_unlock();
+
+ return 0;
+err_unlock:
+ rcu_read_unlock();
+err_cancel_msg:
+ genlmsg_cancel(msg, hdr);
+err_free_msg:
+ nlmsg_free(msg);
+ return ret;
+}
+
/**
* ovpn_nl_register - perform any needed registration in the NL subsustem
*
@@ -12,4 +12,6 @@
int ovpn_nl_register(void);
void ovpn_nl_unregister(void);
+int ovpn_nl_key_swap_notify(struct ovpn_peer *peer, u8 key_id);
+
#endif /* _NET_OVPN_NETLINK_H_ */
IV wrap-around is cryptographically dangerous for a number of ciphers, therefore kill the key and inform userspace (via netlink) should the IV space go exhausted. Userspace has two ways of deciding when the key has to be renewed before exhausting the IV space: 1) time based approach: after X seconds/minutes userspace generates a new key and sends it to the kernel. This is based on guestimate and normally default timer value works well. 2) packet count based approach: after X packets/bytes userspace generates a new key and sends it to the kernel. Userspace keeps track of the amount of traffic by periodically polling GET_PEER and fetching the VPN/LINK stats. Signed-off-by: Antonio Quartulli <antonio@openvpn.net> --- drivers/net/ovpn/crypto.c | 19 ++++++++++++++ drivers/net/ovpn/crypto.h | 2 ++ drivers/net/ovpn/io.c | 13 ++++++++++ drivers/net/ovpn/netlink.c | 64 ++++++++++++++++++++++++++++++++++++++++++++++ drivers/net/ovpn/netlink.h | 2 ++ 5 files changed, 100 insertions(+)